The most common causes of hemorrhoids are straining at bowel movements, prolonged sitting and pregnancy. Internal hemorrhoids occur above the anal sphincter, and external hemorrhoids occur below, outside the anal canal.
Update Date 4/23/2013
Updated by: Joshua Kunin, MD, Consulting Colorectal Surgeon, Zichron Yaakov, Israel. Also reviewed by David Zieve, MD, MHA, Bethanne Black, and the A.D.A.M. Editorial team.